Vernanimalcula guizhouena is an acritarch dating from 600 to 580million years ago; it was between 0.1 and 0.2 mm across (roughly the width of one or two human hairs). Vernanimalcula means "small spring animal", referring to its appearance in the fossil record at the end of the MarinoanGlaciation and the belief upon discovery it was an animal.

The appearance of Vernanimalcula so early in the fossil record was believed to have had important implications if it were really bilaterian. The radiation of animals into many phyla would have occurred before any animal became much larger than microscopic size, making the sudden appearance of many animal phyla in the Cambrian explosion an illusion[1] and merely represented a (geologically) sudden increase in size and the development of easily fossilised body parts by species in existing phyla.[2][3][4][5]

The description of Vernanimalcula as bilaterian has been strongly challenged. Other workers (Bengtson, Budd and co-workers) in the field have repeatedly claimed that Vernanimalcula is largely a taphonomic artefact generated by phosphate growth within a spherical object such as an acritarch, and thus Vernanimalcula was not even an animal, let alone a bilaterian.[6][7] Chen et al. initially defended their interpretation of Vernanimalcula against the claims of Bengtson and Budd.[8] Petryshyn et al. examined additional fossils resembling Vernanimalcula and concluded that the fossils are "likely biogenic in nature."[9]

^Chen, Jun Yuan, Paola Oliveri, Eric Davidson and David J. Bottjer. 2004. Response to Comment on "Small Bilaterian Fossils from 40 to 55 Million Years Before the Cambrian". At [1] - Retrieved June 20, 2007